SX50 HS Users: Ask for Technique Suggestion

I just bought Canon SX50 yesterday.

1. I tried to use AV, and I found that the shutter speed was limited to 1s or faster even I mounted the camera on tripod. Is there any solution to set the shutter speed slower than 1s in the AV mode?

2. In HDR mode, I cannot manually set the ISO speed. How can I set ISO manually?

Thanks!